Buggy code:
public abstract class Page extends MarkupContainer implements IRedirectListener { protected static final boolean ACCESS_ALLOWED = true ; protected static final boolean ACCESS_DENIED = false ; private static final byte FLAG_IS_RENDERING = 64 ; private static final byte FLAG_NEW_VERSION = 16 ; private static final byte FLAG_TRACK_CHANGES = 32 ; private static final Log log = LogFactory . getLog ( Page . class ) ; private int autoIndex ; private IFeedback feedback ; private FeedbackMessages feedbackMessages ; private int id = - 1 ; private transient PageMap pageMap ; private String pageMapName ; private transient Set renderedComponents ; private transient Session session = null ; private IPageVersionManager versionManager ; protected Page ( ) { } protected Page ( final IModel model ) { } public final boolean continueToOriginalDestination ( ) { } public int getAutoIndex ( ) { } public final int getCurrentVersionNumber ( ) { } public FeedbackMessages getFeedbackMessages ( ) { } public final String getId ( ) { } public final Iterator getPageSets ( ) { } public final Session getSession ( ) { } public Page getVersion ( final int versionNumber ) { } public PageState newPageState ( ) { } public final void onRedirect ( ) { } public final void redirectToInterceptPage ( final Page page ) { } public final void removePersistedFormData ( final Class formClass , final boolean disablePersistence ) { } public final void request ( ) { } public void setFeedback ( final IFeedback feedback ) { } public final void setPageMap ( final String pageMapName ) { } public String toString ( ) { } public abstract String urlFor ( final Component component , final Class listenerInterface ) { } public abstract String urlFor ( final String path ) { } public abstract String urlFor ( final String pageMapName , final Class pageClass , final PageParameters parameters ) { } protected boolean checkAccess ( ) { } protected void configureResponse ( ) { } protected PageMap getPageMap ( ) { } protected IModel initModel ( ) { } protected final void internalOnBeginRequest ( ) { } protected final void internalOnEndRequest ( ) { } protected final void internalOnModelChanged ( ) { } protected IPageVersionManager newVersionManager ( ) { } protected final void onRender ( ) { } final void componentAdded ( final Component component ) { } final void componentModelChanging ( final Component component ) { } final void componentRemoved ( final Component component ) { } final void componentVisibilityChanged ( final Component component ) { } final void componentRendered ( final Component component ) { } final void resetMarkupStreams ( ) { } final void setId ( final int id ) { } private final void checkModification ( ) { } private final void checkRendering ( ) { visitChildren ( new IVisitor ( ) { public Object component ( final Component component ) { if ( ( ( renderedComponents ) == null ) || ( ! ( renderedComponents . contains ( component ) ) ) ) { <START_BUG> throw new WicketRuntimeException ( component . exceptionMessage ( ( "Component<seq2seq4repair_space>never<seq2seq4repair_space>rendered.<seq2seq4repair_space>You<seq2seq4repair_space>probably<seq2seq4repair_space>failed<seq2seq4repair_space>to<seq2seq4repair_space>" + "reference<seq2seq4repair_space>it<seq2seq4repair_space>in<seq2seq4repair_space>your<seq2seq4repair_space>markup." ) ) ) ; <END_BUG> } return CONTINUE_TRAVERSAL ; } } ) ; renderedComponents = null ; } private void init ( ) { } private final void newVersion ( ) { } }

Fix:
throw new WicketRuntimeException ( component . exceptionMessage ( ( "Component<seq2seq4repair_space>never<seq2seq4repair_space>rendered.<seq2seq4repair_space>You<seq2seq4repair_space>probably<seq2seq4repair_space>failed<seq2seq4repair_space>to<seq2seq4repair_space>" + "reference<seq2seq4repair_space>it<seq2seq4repair_space>in<seq2seq4repair_space>your<seq2seq4repair_space>markup" ) ) ) ;